Fibers based on synthetic organic polymers have revolutionized the textile industry. One manufacturing method of fiber formation is melt spinning, in which synthetic polymer is heated above its melting point, the molten polymer is forced through a spinneret (a die with many small orifices), and the jet of molten polymer emerging from each orifice is guided to a cooling zone where the polymer solidifies. In most instances the filaments formed by melt spinning are not suitable textile fibers until they have been subjected to one or more successive drawing operations. Drawing is the hot or cold stretching and attenuation of fiber filaments to achieve an irreversible extension and to develop a fine fiber structure. Typical textile fibers have linear densities in the range of 3 to 15 denier. Fibers in the 3 to 6 denier range are generally used in nonwoven materials as well as in woven and knitted fabrics for use in apparel. Coarser fibers are generally used in carpets, upholstery, and certain industrial textiles. A recent development in fiber technology is the category of microfibers with linear densities &lt;0.11 tex (1 denier). Bicomponent fibers, where two different polymers are extruded simultaneously in either side-by-side or skin/core configurations, are also an important category of fibers. Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Ed., John Wiley & Sons, N.Y., Vol. 10, 1993, "Fibers," pp. 541, 542, 552.
A type of bicomponent fiber is the bicomponent binder fiber, the historical paper by D. Morgan which appears in INDA Journal of Nonwoven Research, Vol. 4(4), Fall 1992, pp. 22-26. This review article says it is worth noting that the majority of bicomponent fibers so far made have been side-by-side acrylics used in knitwear garments to provide bulk. Table 1 of this review article lists suppliers of various bicomponent fibers, which are of relatively low denier, ranging from about 1 to up to 20.
U.S. Pat. No. 4,839,439 (McAvoy et al.) and U.S. Pat. No. 5,030,496 (McGurran) describe nonwoven articles prepared by blending melt bondable, bicomponent sheath/core, polyester, staple fibers having a denier of six and larger, for example 15, with synthetic, organic, staple fibers, forming a nonwoven web from the blend, heating the web to cause the melt bondable staple fibers to initially bond, or prebond, the web, coating the web with a binder resin, and drying and heating the coated web.
U.S. Pat. No. 5,082,720 (Hayes) discusses prior art relating to nonwoven webs of bicomponent melt-bondable fibers. The invention of the Hayes patent is directed to drawn or oriented, melt-bondable, bicomponent filaments or fibers of 1 to 200 denier formed by the co-spinning of at least two distinctive polymer components, e.g., in a sheath-core or side-by-side configuration, immediately cooling the filaments after they are formed, and then drawing the filaments. The first component is preferably at least partially crystalline polymer and can be polyester, e.g., polyethylene terephthalate; polyphenylenesulfide; polyamide, e.g., nylon; polyimide; polyetherimide; and polyolefin, e.g., polypropylene. The second component comprises a blend of certain amounts of at least one polymer that is at least partially crystalline and at least one amorphous polymer, where the blend has a melting point of at least 130.degree. C. and at least 30.degree. C. below the melting point of the first component. Materials suitable for use as the second component include polyesters, polyolefins, and polyamides. The first component can be the core and the second component can be the sheath of the bicomponent fiber.
Filaments of poly(vinylchloride) ("PVC," or simply "vinyl"), a synthetic thermoplastic polymer, are used to make open or porous, nonwoven, three-dimensional, fibrous mats or matting. The mats are used for covering any of a variety of floors or walking surfaces, such as those of office building, factory, and residential entry-ways or foyers and hallways, areas around swimming pools, and machine operator stations, to remove and trap dirt and water from the bottom (soles and heels) of shoes, protect floors and carpets, reduce floor maintenance, and provide safety and comfort. Generally the mats are open or porous webs of interengaged or intertwined, usually looped, sinuous, or coiled, coarse or large-diameter fibers (or filaments); such fibers are typically melt-extruded from plasticized PVC into single-component fibers which are aggregated and bonded (usually with an applied binder coating or adhesive). An example of commercially-available matting product is Nomad.TM. matting constructed of interengaged loops of vinyl filaments that are bonded together and may be supported on and adhered to a backing--see product bulletins 70-0704-2684-4 and 70-0704-2694-8 of the 3M Company, St. Paul, Minn., U.S.A.
Relatively early patents describing matting made from various thermoplastics including PVC are U.S. Pat. No. 3,837,988 (Hennen et al.), U.S. Pat. No. 3,686,049 (Manner et al.), U.S. Pat. No. 4,351,683 (Kusilek), and U.S. Pat. No. 4,634,485 (Welygan et al.). Common aspects of the method described in these patents, briefly stated, comprises extruding continuous filaments of thermoplastic polymer downward toward and into a water quench bath where a web of interengaged, integrated, or intermingled and spot-bonded filaments is formed. The web can be subsequently treated with bonding agent or resin to improve bonding, strength, or integration. Typically, in the absence of a bonding agent or resin applied and cured subsequent to the web-forming step, the filaments of the web exhibit a tensile strength much greater than that of the spot-bond itself. That is, as a result of tensile force applied to the web after spot welding but before application of a subsequent bonding treatment, the fibers of the web will separate at the sites of interfilament bonding more frequently than the fibers will break.
Recently poly(vinyl chloride) has been said to be environmentally undesirable because its combustion products include toxic or hazardous hydrogen chloride fumes. It has been reported that the existing use of PVC in Sweden should be phased out by the year 2000--see European Chemical News, Jul. 4, 1994, p. 23. One Swedish commercial enterprise stated it plans to stop making PVC-based elastic flooring and launch a new, PVC-free flooring--see Plastic Week, Aug. 9, 1993. Thus attention is being directed to alternatives for PVC.
Bicomponent fibers and multicomponent fibers are described in Kirk-Othmer Encyclopedia of Chemical Technology, Third Ed., Supplement Vol., 1984, pp. 372-392, and Encyclopedia of Polymer Science and Technology, John Wiley & Sons, N.Y., Vol. 6, 1986, pp. 830, 831. Patents describing certain multicomponent or bicomponent fibers include U.S. Pat. Nos. 3,589,956 (Kranz et al.), 3,707,341 (Fontijn et al.), 4,189,338 (Ejima et al.), 4,211,819 (Kunimune), 4,234,655 (Kunimune et al.), 4,269,888 (Ejima et al.), 4,406,850 (Hills), 4,469,540 (Jurukawa et al.), 4,500,384 (Tomioka et al.), 4,552,603 (Harris et al.), 5,082,720 (Hayes), 5,336,552 (Strack et al.). The process of manufacture of multicomponent fibers and a general discussion of the method of extrusion of these fibers are also described in Kirk-Othmer, Third Ed., loc. cit. Some patents describing spinneret assemblies for extruding bicomponent fibers of the sheath-core type are U.S. Pat. Nos. 4,052,146 (Sternberg), 4,251,200 (Parkin), 4,406,850 (Hills), and PCT International Appln. published as WO 89/02938 (Hills Res. & Devel. Inc.).
Some other patent filings, viz., U.S. Pat. Nos. 3,687,759 (Werner et al.) and 3,691,004 (Werner et al.), though they do not describe PVC matting, describe mattings of filaments of substantially amorphous polymer, such as polycaprolactam, which are formed by melt spinning into a liquid quench bath in such a manner that the filaments lie in the form of overlapping loops randomly bonded at their points of contact as they solidify in the bath. These patents state that preferably the filaments are spun, looped, and bonded without any substantial tension being placed on the filaments, or that it is preferable to avoid any substantial tension capable of stretching the filaments as they are withdrawn through the cooling bath so that the amorphous character of the initial polymer is largely retained. Matting articles which are formed without spinning into a liquid quench bath and consisting essentially of melt-spun filaments which are self bonded or fused at random points of intersection without using any bonding agent have been described in U.S. Pat. No. 4,252,590 (Rasen et al.).
A series of patents issued to Yamanaka et al., viz., U.S. Pat. Nos. 4,859,516, 4,913,757, and 4,95,265, describe various mats consisting of filament loop aggregations formed by extruding thermoplastic synthetic resin vertically toward the surface of a cooling bath of water at a speed regulated by guide rollers disposed in the water (to which a surface active agent can be added), the density of the aggregations of the resulting bonded or fused aggregations being regulated in certain manners.